1. Field of the Invention
The present invention relates to a constant detecting apparatus for a brushless DC motor for detecting the inductance of a brushless DC motor comprising a rotor that has a permanent magnet and a stator that generates a rotating magnetic field that causes the rotation of the rotor, a control apparatus for a brushless DC motor, and a program for detecting the constant of a brushless DC motor.
2. Description of the Related Art
Conventionally, vehicles such as electric vehicles and hybrid vehicles are known that have installed a brushless DC motor using a permanent magnet to provide a magnetic field as a power source for vehicle travel.
A control apparatus for this kind of brushless DC motor is known that carries out feedback control such that, for example, a phase current supplied to each phase of a brushless DC motor is measured, and the measured value of the phase current is converted to an orthogonal coordinate system that rotates in synchronism with the rotor. The orthogonal coordinate system comprises, for example, a d axis current and a q axis current on a dq coordinate system where the direction of the flux of the rotor is the d axis (the torque axis) and the direction orthogonal to this d axis is the q axis (the magnetic field axis). In this control apparatus, the feedback control is carried out so that the difference between the command value and the measured value of the current is zero on this dq coordinate system.
Specifically, the d axis voltage command value and the q axis voltage command value on the dq coordinate system are calculated, for example, by a proportional integration (PI) operation from the differences between the command value and the observed value of the current on the dq coordinate axis, that is, the d axis current difference and the q axis current difference. Next, each of the voltage command values for the phase voltage supplied to each of, for example, three phases (the U phase, the V phase, and the W phase) of the brushless DC motor are calculated from the d axis voltage command value and the q axis voltage command value. In addition, each of these voltage command values is input as a switching command to the inverter formed by switching elements such as insulated-gate bipolar transistors (IGBTs), and the alternating current power for driving the brushless DC motor is output from the inverter depending on these switching commands.
In a control apparatus for a brushless DC motor according to the one example of the conventional art described above, a method is known wherein, for example, the d axis inductance and q axis inductance are calculated as parameters when the d axis current command value and the q axis current command value are calculated based on the torque command that depends on how much the driver of the vehicle maneuvers the accelerator.
However, in the control apparatus of the brushless DC motor described above, because of the presence, for example, of the phase delay characteristic of the position sensor for detecting the electromagnetic pole position of the rotor, there is the case in which the signal of the position sensor that represents a predetermined reference position presents a value that has shifted with respect to the true reference position as the number of rotations increases. Due to the shifting of the position sensor, there are the problems that errors occur in the phases of each of the current phases and the phases of each of the voltage phases, and that errors occur in the results of the calculation of the d axis inductance and the q axis inductance.
In addition, while the brushless DC motor is being rotated, the winding resistance value fluctuates along with the fluctuations in the temperature of the windings that are wound around the rotor, the induced voltage fluctuates along with the fluctuations in the temperature of the permanent magnet of the rotor, the iron loss fluctuates, or the like, and thereby there are the problems that errors occur in the voltage vector, and that errors occur in the results of the calculation of the d axis inductance and the q axis inductance.
Here, in the case that the d axis current command value and the q axis current command value are calculated based on a d axis inductance and a q axis inductance that include these errors, there are the problems that the precision of the initial response decreases, and that the responsiveness during feedback control deteriorates. Furthermore, because the actual operating condition cannot be adequately known, there is the concern that inconveniences such as a decrease in the operating efficiency and excess current may occur.
In addition, in methods that estimate each of the inductances by taking into consideration the amount of transient fluctuation of the d axis inductance and the q axis inductance, there are the problems that the amount of required memory must be increased in order to store each type of control data. In addition, the calculation processing becomes complex, the scale of the control apparatus increases, and the necessary cost is increased when the control apparatus is configured.
In consideration of the above-described problems, it is an object of the present invention to provide a constant detecting apparatus for a brushless DC motor wherein the necessary cost originating in configuring the apparatus and the programs is decreased and the initial response precision and readiness during control is increased, control apparatus for the brushless DC motor, and a program for detecting the constant of a brushless DC motor.
In order to attain the object of solving the above-described problems, in a first aspect of the present invention, a constant detecting apparatus for a brushless DC motor for detecting the inductance of a brushless DC motor comprising a rotor that has a permanent magnet and a multiphase stator that generates a rotating magnetic field that causes the rotation of the rotor is characterized in comprising a phase voltage detecting device (for example, the phase voltage detector 46 in the embodiment described below) for detecting the phase angle and the effective value of the phase voltage of the brushless DC motor and a phase current detecting device (for example, the phase current detector 47 in the embodiment described below) for detecting the phase angle and the effective value of the phase current and a position detecting device (for example, the position sensor 43 in the embodiment described below) for detecting the phase angle of the induced voltage from the magnetic pole position of the rotor and a rotation number detecting device (for example the rotation sensor 41 in the embodiment described below) for detecting the number of rotations; a phase resistance value calculating device (for example, step S 12 in the embodiment described below) for calculating the phase resistance value based on the temperature of the brushless DC motor and an induced voltage constant calculating device (for example, step S 24 in the embodiment described below) for calculating the induced voltage constant; a phase difference calculating device (for example, step S 14 and step S 17 in the embodiment described below) for calculating the voltage phase difference comprising the difference between the phases of the induced voltage and phase voltage and the current phase difference comprising the difference between the phases of the induced voltage and the phase current; a phase compensating value calculating device (for example, the step S 16 in the embodiment described below) for calculating the phase compensating value that compensates the voltage phase difference and the current phase difference based on the number of rotations; an iron loss calculating device (for example, steps S 20 to step S 27 in the embodiment described below) for calculating the iron loss of the brushless DC motor; an effective phase current calculating device (step S 28 in the embodiment described below) for calculating the effective phase current based on the iron loss by subtracting the iron loss component from the phase current; and an inductance calculating device (for example step S 29 in the embodiment described below) for calculating the magnetic field axis inductance and the torque axis inductance based on the phase resistance value, the number of rotations, the induced voltage constant, the voltage phase difference, the current phase difference, the phase compensating value, and the effective phase current.
According to the constant detecting device for a brushless DC motor having the structure described above, the copper loss can be suitably calculated by calculating the phase resistance value that depends on the temperature change of the brushless DC motor while rotating. Furthermore, a suitable induced voltage can be calculated by multiplying the induced voltage constant found by searching a map, for example, and an accurate number of rotations detected by the rotating number detecting device, which depends on the temperature change of the brushless DC motor while rotating.
Furthermore, an increase in the error caused by the phase delay characteristics of the position detecting device can be prevented by compensating the voltage phase error and the current phase error detected by the position detecting device depending on the number of rotations. Furthermore, a suitable phase current can be calculated depending on the actual operating state of the brushless DC motor by calculating the iron loss of the brushless DC motor during rotation and subtracting the iron loss component from the phase current detected by the phase current detecting device.
In this manner, each inductance can be calculated with high precision taking into consideration the fluctuation of the copper loss, the fluctuation of the induced voltage, the detected error due to the phase delay of the position detecting device, and the discrepancy in the phase current due to the iron loss by calculating the magnetic field axis inductance and the torque axis inductance based on the calculated phase resistance value, the induced voltage constant, the voltage phase difference and current phase difference, the phase compensating value, and the effective phase current.
In a second aspect of the present invention, a constant detecting apparatus for a brushless DC motor according to the first aspect comprises an output torque detecting device (for example, the torque sensor 42 in the embodiment described below) for detecting the output torque of the brushless DC motor, and wherein the iron loss calculating device comprises a motor power calculating device (for example, step S 20 in the embodiment described below) for calculating the motor output power and the motor input power of the brushless DC motor based on the output torque and the number of rotations; a copper loss calculating device (for example, step S 21 in the embodiment described below) for calculating the copper loss based on the phase resistance value and the phase current; a total motor loss calculating device (for example, step S 22 of the embodiment described below) calculates the total motor loss by subtracting the motor output power from the motor input power; a mechanical loss calculating device (for example, step S 23 in the embodiment described below) for calculating the mechanical loss of the brushless DC motor; a subtracting device (for example, step S 26 in the embodiment describe below) for calculating the iron loss by subtracting the copper loss and the mechanical loss from the total motor loss; and an equivalent resistance value calculating device (for example, step S 27 in the embodiment described below) for calculating the measured iron loss equivalent resistance value based on the effective value of the phase voltage that includes all frequency components and the iron loss.
According to the constant calculating device of the brushless DC motor having the structure described above, the effective phase current that does not include the iron loss component can be easily calculated from the phase current detected by the phase current detecting device by calculating the iron loss by subtracting the copper loss and the mechanical loss from the total loss of the brushless DC motor, and then calculating the iron loss equivalent resistance value for the phase voltage from this iron loss.
Here, a suitable mechanical loss that depends on the state of actual operating state of the brushless DC motor can be obtained by setting in advance a predetermined map or the like that depends, for example, on the number of rotations.
Furthermore, in a third aspect of the present invention, the constant detecting device for a brushless DC motor is characterized in that the phase resistance value calculating device calculates the phase resistance value based on the temperature of the stator windings, and the induced voltage constant calculating device calculates the induced voltage constant based on the temperature of the rotor.
According to the constant detecting device for a brushless DC motor having the structure described above, in the brushless DC motor during rotation, a phase resistance value that increases along with the increase in the winding temperature can be suitably calculated, and at the same time an induced voltage that changes with a decreasing tendency along with the increase in the temperature of the permanent magnet used to provide the magnetic field can be suitably calculated.
Here, in the case that the induced voltage is calculated, the induced voltage can be easily calculated by setting in advance a predetermined map or the like for the induced voltage constant that changes depending on the temperature of the rotor, and multiplying the induced voltage constant obtained by the map search by the number of rotations.
In addition, in a fourth aspect of the present invention, the constant detecting device for a brushless DC motor comprising a rotor that has a permanent magnet and a multiphase stator that generates a rotating magnetic field that causes the rotation of the rotor, and is rotated by an electric switching device (for example, the inverter 13 in the embodiment described below) is characterized in comprising a phase voltage detecting device (for example, the phase voltage detector 46 in the embodiment described below) for detecting the phase angle and the effective value of the phase voltage of the brushless DC motor and a phase current detecting device (for example, the phase current detector 47 in the embodiment described below) for detecting the phase angle and the effective value of the phase current and a position detecting device (for example, the position sensor 43 in the embodiment described below) for detecting the phase angle of the induced voltage from the magnetic pole position of the rotor and a rotation number detecting device (for example the rotation sensor 41 in the embodiment described below) for detecting the number of rotations; a phase resistance value calculating device (for example, step S 12 in the embodiment described below) for calculating the phase resistance value based on the temperature of the brushless DC motor; a phase difference calculating device (for example, step S 14 and step S 17 in the embodiment described below) for calculating the voltage phase difference that comprises the difference between the phases of the induced voltage and phase voltage and the current phase difference comprising the difference between the phases of the induced voltage and phase current; a phase compensating value calculating device (for example, the step S 16 in the embodiment described below) for calculating the phase compensating value that compensates the voltage phase difference and the current phase difference; an iron loss calculating device (for example, steps S 20 to step S 27 in the embodiment described below) for calculating the iron loss of the brushless DC motor during rotation; an effective phase current calculating device (step S 28 in the embodiment described below) for calculating the effective phase current based on the iron loss by subtracting the iron loss component from the phase current; a power supply interrupting device (for example, the interruption circuit 56 in the embodiment described below) that temporarily interrupts the power supply to the brushless DC motor from the electric switching device; and an inductance calculating device (for example step S 29 in the embodiment described below) for detecting the voltage value of the induced voltage by the phase voltage detecting device during the power supply interruption due to the power supply interruption device, and calculates the magnetic field axis inductance and the torque axis inductance based on the phase resistance value, the voltage value of the induced voltage, the voltage phase difference, the current phase difference, the phase compensating value, and the effective phase current.
According to the constant detecting apparatus for a brushless DC motor having the structure described above, when calculating the magnetic field axis inductance and the torque axis inductance based on the detected signals of each of the detecting device and taking into consideration the fluctuation in the copper loss, the fluctuation in the induced voltage, the detected error due to the phase delay of the position detecting device, and the discrepancy of the phase current due to the iron loss, the induced voltage can be directly detected by the phase voltage detecting device by temporarily interrupting the power supply from the electrical switching device that rotates the brushless DC motor.
Thereby, the magnetic field axis inductance and the torque axis inductance can be calculated with high precision depending on the state of actual operation of the brushless DC motor.
In addition, in a fifth aspect of the present invention, the constant detecting apparatus of the brushless DC motor comprising a rotor that has a permanent magnet and a stator having multiphase stator windings that generate a rotating field that rotates this rotor, and detects the inductance of the brushless DC motor rotated by an electric switching device (for example, the inverter 13 in the embodiment described below) is characterized in comprising a winding temperature detecting device (for example the winding temperature sensor 45 in the embodiment described below) for detecting the temperature of the rotor windings; a rotor temperature detecting device (for example, the rotor temperature sensor 44 in the embodiment described below) for detecting the temperature of the rotor; a phase voltage detecting device (for example, the phase voltage detector 46 in the embodiment described below) for detecting the phase angle and the effective value of the phase voltage; a phase current detecting device (for example, the phase current detector 47 in the embodiment described below) for detecting the phase angle and the effective value of the phase current; a position detecting device (for example, the position sensor 43 in the embodiment described below) for detecting the phase angle of the induced voltage from the magnetic pole position of the rotor; a rotation number detecting device (for example, the rotation sensor 41 in the embodiment described below) for detecting the number of rotations; an output torque detecting device (for example, the torque sensor 42 in the embodiment described below) for detecting the output torque; a phase difference detecting device (for example step S 14 and step S 17 in the embodiment described below) for calculating the voltage phase difference comprising the difference between the phases of the induced voltage and the phase voltage and the current phase difference comprising the difference between the phases of the induced voltage and the phase current; a storage device (for example, memory 28 in the embodiment described below) that stores the winding resistance value of the windings and the wiring resistance value of the connecting wiring of the brushless DC motor at a predetermined temperature, the voltage phase difference set in advance depending on the number of rotations and the mechanical loss that is set in advance depending on the compensated value of the current phase difference and the number of rotations, and the induced voltage constant set in advance depending on the temperature of the rotor; a phase resistance value calculating device (for example, step S 12 in the embodiment described below) for calculating the phase resistance value of the brushless DC motor during rotation based on the winding temperature, the winding resistance value, and the wiring resistance value; a phase difference compensating device (for example, step S 16 to step S 19 in the embodiment described below) for calculating the compensating voltage phase difference and the compensating current phase difference that compensate the current phase difference and the voltage phase difference based on the compensating value; a motor power calculating device (for example, step S 20 in the embodiment described below) for calculating the motor output power and the motor input power of the brushless DC motor based on sad output torque and the number of rotations; a copper loss calculating device (for example, step S 21 in the embodiment described below) for calculating the copper loss based on an effective value that includes the phase resistance value and all frequency components of the phase current; a total motor loss calculating device (for example, step S 22 in the embodiment described below) for calculating the total motor loss by subtracting the motor output power from the motor input power; a subtracting device (for example, step S 26 in the embodiment described below) for calculating the iron loss by subtracting the copper loss and the mechanical loss from the total motor loss; an equivalent resistance value calculating device (for example step S 27 in the embodiment described below) for calculating the measured iron loss equivalent resistance value based on the effective value of the phase voltage that includes all frequency components and the iron loss; an effective phase current calculating device (for example, step S 28 in the embodiment described below) for calculating the effective phase current excluding the iron loss component by subtracting the iron loss component from the effective value of the phase current and an effective phase difference calculating device (for example, step S 28 in the embodiment explained below) for calculating the effective current phase difference excluding the iron core component from the compensating current phase difference based on the magnetic filed axis current value and the torque axis current value of the effective phase current; and an inductance calculating device (for example step S 29 in the embodiment described below) for calculating the magnetic field axis inductance and the torque axis inductance based on the phase resistance value, the number of rotations, the induced voltage constant, the effective phase current, the compensating voltage phase difference, and the effective current phase difference.
According to the constant detecting apparatus for a brushless DC motor having the structure described above, the winding resistance value after temperature compensation can be calculated based on the winding resistance value at a predetermined temperature stored in the storage device and the winding temperature detected during rotation of the brushless DC motor. In addition, the phase resistance value is calculated by adding the calculated winding resistance value and the wiring resistance value stored in the storage device, and the copper loss is calculated by the phase current detected by the phase current detecting device. In addition, the phase resistance value is calculated by adding the calculated winding resistance value and the wiring resistance value stored in the storage device, and calculates the copper loss by the phase current detected by the phase current detecting device. The effective phase current that does not include the iron loss component by calculating the iron loss based on this copper loss and the mechanical loss and the total motor loss stored in the storage device, and then calculating the iron loss equivalent resistance value with respect to the phase voltage.
In addition, using the compensating values of the phases of voltage phase difference and the current phase difference stored in the storage device, the phase differences detected by the phase detecting device are compensated, and then the current phase difference that does not include the iron loss component is calculated. In addition, by calculating the magnetic field axis inductance and the torque axis inductance based on the induced voltage constant stored in the storage device and the phase resistance value, the effective phase current, the compensating voltage phase difference, and the current phase difference calculated based on the detected values, each of the inductances can be calculated with high precision taking into consideration the fluctuations in the copper loss, the discrepancy of the phase current due to iron loss, the detection error due to the phase delay of the position detecting device, and the fluctuations in the induced voltage.
In addition, in a sixth aspect of the present invention, a control apparatus for a brushless DC motor that rotates a brushless DC motor comprising a rotor that has a permanent magnet and a multiphase stator having stator windings that generate a rotating field that rotates this rotor using an electric switching device (for example, the inverter 13 in the embodiment described below) that sequentially commutes the electricity to the stator winding that comprises a plurality of switching elements characterized in comprising a phase voltage detecting device (for example, the phase voltage detector 46 in the embodiment described below) for detecting the phase angle and the effective value of the phase voltage of the brushless DC motor and a phase current detecting device (for example, the phase current detector 47 in the embodiment described below) for detecting the phase angle and the effective value of the phase current and a position detecting device (for example, the position sensor 43 in the embodiment described below) for detecting the phase angle of the induced voltage from the magnetic pole position of the rotor and a rotation number detecting device (for example the rotation sensor 41 in the embodiment described below) for detecting the number of rotations; a phase resistance value calculating device (for example, step S 12 in the embodiment described below) for calculating the phase resistance value based on the temperature of the brushless DC motor and an induced voltage constant calculating device (for example, step S 24 in the embodiment described below) for calculating the induced voltage constant; a phase difference calculating device (for example, step S 14 and step S 17 in the embodiment described below) for calculating the voltage phase difference comprising the difference between the phases of the induced voltage and the phase current and the current phase difference comprising the difference between the phases of the induced voltage and phase current; a phase compensating value calculating device (for example, the step S 16 in the embodiment described below) for calculating the phase compensating value that compensates the voltage phase difference and the current phase difference based on the number of rotations; an iron loss calculating device (for example, steps S 20 to step S 27 in the embodiment described below) for calculating the iron loss of the brushless DC motor during rotation; an effective phase current calculating device (step S 28 in the embodiment described below) for calculating the effective phase current based on the iron loss by subtracting the iron loss component from the phase current; an inductance calculating device (for example step S 29 in the embodiment described below) for calculating the magnetic field axis inductance and the torque axis inductance based on the phase resistance value, the number of rotations, the induced voltage constant, the voltage phase difference, the current phase difference, the phase compensating value, and the effective phase current; a torque command input device (for example, the torque command calculating unit 21 in the embodiment described below) that inputs the torque command value; a current command value calculating device (for example, the target current calculating unit 22 in the embodiment described below) for calculating the magnetic field axis current command value and the torque axis current command value based on the induced voltage constant, the magnetic field axis inductance, the torque axis inductance, and the torque command value; and a pulse width modulated signal output device (for example, the feedback control unit 23 in the embodiment described below) that outputs a pulse width modulated signal to the electric switching device based on the magnetic field axis current command value and the torque axis current command value.
According to control apparatus for the brushless DC motor having the structure described above, a suitable copper loss can be suitably calculated by calculating the phase resistance value that depends on the temperature change of the brushless DC motor during rotation. Furthermore, a suitable induced voltage that depends on the temperature change of the brushless DC motor during rotation can be calculated by multiplying the induced voltage constant found, for example, by searching a map, and the number of rotations detected by a rotation detecting device.
Furthermore, the increase in the error caused by the phase delay property of the position detecting device can be prevented by compensating the voltage phase difference and the current phase difference detected by the position detecting device depending on the number of rotations. Furthermore, a suitable phase current can be calculated that depends on the actual operating state of the brushless DC motor by calculating the iron loss of the brushless DC motor during rotation and subtracting the iron loss component from the phase current detected by the phase current detecting device.
Each inductance can be calculated with high precision taking into consideration the fluctuation of the copper loss, the fluctuation in the induced voltage, the detected difference due to the phase delay of the position detecting device, and the discrepancy in the phase current due to the iron loss by calculating the magnetic field axis inductance and the torque axis inductance based on the phase resistance value, induced voltage, the voltage phase difference and the current phase difference, the phase compensating value, and the effective phase current.
Thereby, during the control of the brushless DC motor, the correct magnetic field axis current command value and the torque axis current command value that depend on the torque command value can be calculated, and the initial response precision can be improved. Furthermore, feedback control can be carried out based on the effective phase current that does not include the iron loss component, and the responsiveness and operational effectiveness during control can be improved.
Furthermore, because the calculation processing is carried out using many detected valued that have been measured by each of the detecting devices, for example, it is possible to prevent increasing the amount of memory required to store the control data and prevent increasing the scale of the control apparatus due to the increasing complexity of the calculating processing, and thereby contribute to the elimination of the costs required when constructing the control apparatus.
In addition, in a seventh aspect of the present invention, a control apparatus for a brushless DC motor is characterized in comprising an output torque detecting device (for example, the torque sensor 42 in the embodiment described below) for detecting the output torque of the brushless DC motor, and wherein the iron loss calculating device comprises a motor power calculating device (for example, step S 20 in the embodiment described below) for calculating the motor output power and the motor input power of the brushless DC motor based on the output torque and the number of rotations; a copper loss calculating device (for example, step S 21 in the embodiment described below) for calculating the copper loss based on the phase resistance value and the phase current; a total motor loss calculating device (for example, step S 22 in the embodiment described below) for calculating the total motor loss by subtracting the motor output power from the motor input power; a mechanical loss calculating device (for example step S 23 in the embodiment described below) for calculating the mechanical loss of the brushless DC motor; a subtracting device (for example, step 26 in the embodiment described below) for calculating the iron loss by subtracting the copper loss and the mechanical loss from the total motor loss; and an equivalent resistance value calculating device (for example, step S 27 in the embodiment described below) for calculating the measured iron loss equivalent resistance value based on the effective value of the phase voltage that include all frequency components and the iron loss.
According to the control apparatus for the brushless DC motor having the structure described above, the effective phase current that does not include the iron loss component for the phase current detected by the phase current detecting device can be easily calculated by calculating the iron loss by subtracting the copper loss and the mechanical loss from the total loss of the brushless DC motor and calculating the iron loss equivalent resistance value for the phase voltage from this iron loss.
Here, a suitable mechanical loss that depends on the actual operating state of the brushless DC motor can be obtained by setting in advance a predetermined map or the like that depends, for example, the number of rotations.
Furthermore, in an eighth aspect of the present invention, a control apparatus for a brushless DC motor is characterized that the phase resistance value calculating device calculates the phase resistance value based on the temperature of the stator windings, and the induced voltage constant calculating device calculates the induced voltage constant based on the temperature of the rotor.
According to the control apparatus of the brushless DC motor having the structure described above, while the brushless DC motor is rotating, the phase resistance value that increases along with the increase in the winding temperature can be suitably calculated, and in addition, an induced voltage that decreases along with the increase on the temperature of the permanent magnet used for the magnetic field can be suitably calculated.
Here, in the case that the induced voltage is calculated, the induced voltage can be easily calculated by setting in advance a predetermined map or the like for the induced voltage constant that changes depending, for example, on the temperature of the rotor, and multiplying the number of rotations by the induced voltage constant obtained by a map search.
Furthermore, in a ninth aspect of the present invention, a control apparatus for a brushless DC motor that rotates a brushless DC motor comprising a rotor that has a permanent magnet and a multiphase stator having stator windings that generate a rotating field that rotates this rotor using an electric switching device (for example, the inverter 13 in the embodiment described below) that sequentially commutes the electricity to the stator winding that comprises a plurality of switching elements characterized in comprising a phase voltage detecting device (for example, the phase voltage detector 46 in the embodiment described below) for detecting the phase angle and the effective value of the phase voltage of the brushless DC motor and a phase current detecting device (for example, the phase current detector 47 in the embodiment described below) for detecting the phase angle and the effective value of the phase current and a position detecting device (for example, the position sensor 43 in the embodiment described below) for detecting the phase angle of the induced voltage from the magnetic pole position of the rotor and a rotation number detecting device (for example the rotation sensor 41 in the embodiment described below) for detecting the number of rotations; a phase resistance value calculating device (for example, step S 12 in the embodiment described below) for calculating the phase resistance value based on the temperature of the brushless DC motor; a phase compensating value calculating device (for example, the step S 16 in the embodiment described below) for calculating the phase compensating value that compensates the voltage phase difference and the current phase difference; an iron loss calculating device (for example, steps S 20 to step S 27 in the embodiment described below) for calculating the iron loss of the brushless DC motor during rotation; an effective phase current calculating device (for example, step S 28 in the embodiment described below) for calculating the effective phase current by subtracting the iron loss component from the phase current based on the iron loss; a power supply interrupting device (for example, the interrupting circuit 56 in the embodiment described below) that temporarily interrupts the power source from the electric switching device to the brushless DC motor; an inductance calculating device (for example step S 29 in the embodiment described below) for detecting the voltage value of the induced voltage by the phase voltage detecting device during the power supply interruption by the power supply interrupting device, and calculates the magnetic field axis inductance and the torque axis inductance based on the phase resistance value, the voltage value of the induced voltage, the voltage phase difference, the current phase difference, the phase compensating value, and the effective phase current; a torque command input device (for example, the torque command calculating unit 21 in the embodiment described below) that inputs the torque command value; a current command value calculating device (for example, the target current calculating unit 22) for calculating the magnetic field axis current command value and the torque axis current command value based on the induced voltage, the magnetic field axis inductance, the torque axis inductance, and the torque command value; and a pulse width modulated signal output device (for example, the feedback control unit 23 in the embodiment described below) that outputs a pulse width modulated signal to the electric switching device based on the magnetic field axis current command value and the torque axis current command value.
According to the control apparatus for the brushless DC motor having the structure described above, the induced voltage can be directly detected by phase voltage detecting device, and at the same time, the actual rotation angle can be directly detected by the rotation angle detecting device by temporarily interrupting the power supply from the electric switching device that rotates the brushless DC motor when calculating the magnetic field axis inductance and torque axis inductance that takes into consideration the fluctuation in the copper loss, the fluctuation of induced voltage, and detection error due to the phase delay of the rotation angle detecting device, and the discrepancy in the phase voltage due to the iron loss based on detected signals from each of the detecting device.
Thereby, a magnetic field axis inductance and the torque axis inductance can be calculated with high precision that depends on the actual operational state of the brushless DC motor.
Furthermore, in a tenth aspect of the present invention, a control apparatus for a brushless DC motor that rotates a brushless DC motor comprising a rotor that has a permanent magnet and a multiphase stator having stator windings that generate a rotating field that rotates this rotor using an electric switching device (for example, the inverter 13 in the embodiment described below) that comprises a plurality of switching elements and sequentially commutes the electricity to the stator winding, comprises in order to detect the rotating brushless CD motor by said electric switching device a winding temperature detecting device (for example the winding temperature sensor 45 in the embodiment described below) for detecting the temperature of the stator winding by the electric switching device and a rotor temperature detecting device (for example, the rotor temperature sensor 44 in the embodiment described below) for detecting the temperature of the rotor and a phase voltage detecting device (for example, the phase voltage detector 46 in the embodiment described below) for detecting the phase angle and the effective value of the phase voltage and a phase current detecting device (for example, the phase current detector 47 in the embodiment described below) for detecting the phase angle and the effective value of the phase current and a position detecting device (for example, the position sensor 43 in the embodiment described below) for detecting the phase angle of the induced voltage from the magnetic pole position of the rotor and a rotation number detecting device (for example the rotation sensor 41 in the embodiment described below) for detecting the number of rotations and an output torque detecting device (for example, the torque sensor 42 in the embodiment described below) for detecting the output torque; and further comprises: a phase difference calculating device (for example, step S 14 and step S 17 in the embodiment described below) for calculating the voltage phase difference comprising the difference between the phases of the induced voltage and phase voltage and the current phase difference comprising the differences in the phases of the induced voltage and the phase current; a memory device (for example the memory 28 in the embodiment described below) that stores the winding resistance value of the winding and the wiring resistance value of the connecting wiring of the brushless DC motor at a predetermined temperature, the pre-set voltage phase difference and the compensated value of the current phase differences that depend on the number of rotations, the preset mechanical loss that depends on the number of rotations, and a preset induced voltage constant that depends on the temperature of the rotor; a phase resistance value calculating device (for example, step S 12 in the embodiment described below) for calculating the phase resistance value of the brushless DC motor during rotation based on the winding temperature, the winding resistance value, and the wiring resistance value; a phase difference compensating device (for example, the step S 16 to step S 19 in the embodiment described below) for calculating the compensating voltage phase difference and the compensating current phase difference that compensate the current phase difference and the voltage phase difference based on the compensating value; a motor power calculating device (for example, step S 20 in the embodiment described below) for calculating the motor output power and the motor input power for the brushless DC motor based on the output torque and the number of rotations; a copper loss calculating device (for example, step 21 in the embodiment described below) for calculating the copper loss based on the phase resistance value and effective value that includes all frequency components of the phase current; a total motor loss calculating device (for example, step 22 in the embodiment described below) calculates the total motor loss by subtracting the motor output power from the motor input power; a subtracting device (for example, step S 26 in the embodiment described below) for calculating the iron loss by subtracting the copper loss and the mechanical loss from the total motor loss; an equivalent resistance value calculating device (for example, step S 27 in the embodiment described below) for calculating the measured iron loss equivalent resistance value based on the effective value of the phase voltage that includes all frequency components and the iron loss; an effective phase current calculating device (for example, step 28 in the embodiment described below) for calculating the effective phase current eliminating the iron core component by subtracting the iron loss from the effective value of the phase current based on the measured iron loss equivalent resistance value, and the compensating current phase difference; an effective phase difference calculating device (for example, also step S 28 in the embodiment described below) for calculating the effective current phase difference eliminating the iron loss components from the compensating current phase difference based on the magnetic field axis current value and the torque axis current of the effective phase current; an inductance calculating device (for example, step S 29 in the embodiment described below) for calculating the magnetic field axis inductance and the torque axis inductance based on the phase resistance value, the number of rotations, the induced voltage constant, the effective phase current, the compensating voltage phase difference, and the effective current phase difference; a torque command input device (for example, the torque command calculating unit 21) that inputs the torque command value; a current command value calculating device (for example, the target current calculating unit 22 in the embodiment described below) for calculating the magnetic field axis current command value and the torque axis current command value based on the induced voltage constant, the magnetic field axis inductance, the torque axis inductance, and the torque command value; and a pulse width modulated signal output device (for example, the feedback control unit 23 in the embodiment described below) that outputs a pulse width modulated signal to the electric switching device based on the magnetic field axis current command value and the torque axis current command value.
According to the control apparatus for the brushless DC motor having the structure described above, the winding resistance value after temperature compensation can be calculated based on the winding resistance value at a predetermined temperature stored in the storage device and the winding temperature detecting during rotation of the brushless DC motor. In addition, the phase resistance value is calculated by adding the calculated winding resistance value and the wiring resistance value stored in the storage device and the copper loss is calculated by the phase current detected by the phase current detecting device. The iron loss is calculated based on this copper loss, the mechanical loss stored in the storage device, and the total motor loss. Then the effective phase current that does not include the iron loss component is calculated by calculating the iron loss equivalent resistance value for the phase voltage.
In addition, the detected voltage phase difference and current phase difference are compensated by the compensating value of the phase stored in the storage device, and then the current phase difference that does not include the iron loss component is calculated.
In addition, each of the inductances can be calculated with high precision taking into consideration the fluctuation in the copper loss, the discrepancy in the phase current due to the iron loss, the detected error due to the phase delay of the position detecting device and the fluctuation in the induced voltage by calculating the induced voltage constant and the magnetic field axis inductance and the torque axis inductance based on the phase resistance value, the effective phase current, the compensating voltage phase difference, and the current phase difference.
Thereby, during control of the brushless DC motor, the correct magnetic field axis current command value and the torque axis current command value that depend on the torque command value can be calculated, and the initial response precision can be improved. Furthermore, feedback control can be carried out based on the effective phase current that does not include an iron loss component, and the responsiveness and operational efficiency during control can be improved.
In addition, in an eleventh aspect of the present invention, a constant detecting program for a brushless DC motor for making a computer function as a device for calculating the inductance of a brushless DC motor during rotation is characterized in comprising a phase resistance value calculating device (for example, step S 12 in the embodiment described below) for calculating the phase resistance value, based on the temperature of the brushless motor and an induced voltage constant calculating device (for example, step S 24 in the embodiment described below) for calculating the induced voltage constant; a phase difference calculating device (for example, step S 14 and step S 17 in the embodiment described below) for calculating the voltage phase difference comprising the difference between the phases of the induced voltage and the phase voltage and the current phase difference comprising the difference between the phases of the induced voltage and phase current; a phase compensating value calculating device (for example, the step S 16 in the embodiment described below) for calculating the phase compensating value that compensates the voltage phase difference and the current phase difference based on the number of rotations of the brushless DC motor; an iron loss calculating device (for example, steps S 20 to step S 27 in the embodiment described below) for calculating the iron loss of the brushless DC motor; an effective phase current calculating device (for example, step S 28 in the embodiment described below) for calculating the current value of the effective phase current by subtracting the iron loss component from the phase current of the brushless DC motor based on the iron loss; and an inductance calculating device (for example step S 29 in the embodiment described below) for calculating the magnetic field axis inductance and the torque axis inductance based on the phase resistance value, the number of rotations, the induced voltage constant, the voltage phase difference, the current phase difference, the phase compensating value, and the effective phase current.
According to the program for detecting the constant of the brushless DC motor having the structure described above, the copper loss can be suitably calculated by calculating the phase resistance value that depends on the temperature change of the brushless DC motor during rotation. Furthermore, a suitable induced voltage can be calculated by multiplying the induced voltage constant that depends on the temperature change of the brushless DC motor during rotation, for example, by searching a map, by the number of rotations detected by the rotation number detecting device.
Furthermore, an increase in the error caused by the phase delay characteristics of the position detecting device can be prevented by compensating the voltage phase difference and the current phase difference detected by the position detecting device depending on the number of rotations. Furthermore, a suitable phase current that depends on the actual operating state of the brushless DC motor can be calculated by calculating the iron loss of the brushless DC motor during rotation and subtracting the iron loss component from the phase current detected by the phase current detecting device.
Each of the inductances can be calculated with high precision taking into consideration the fluctuation of the copper loss, the fluctuation of the induced voltage, the detection error due to the phase delay of the position detecting device, and the discrepancy of the phase current due to the iron loss by calculating the magnetic field axis inductance and the torque axis inductance based on the phase resistance value, the induced voltage constant, the phase compensating value, and the effective phase current calculated in this manner.
In addition, in a twelfth aspect of the present invention, a program for detecting the constant of a brushless DC motor that causes a computer to function as a device for calculating the inductance of a brushless DC motor during rotation characterized in that the program comprises a operating data reading device (for example, step S 16, step S 23, and step S 24 in the embodiment described below) that reads as operating data the temperature of the stator windings and the temperature of the rotor of the brushless DC motor, the phase angle and the effective value of the phase voltage, the phase angle and effective value of the phase current, the voltage phase difference comprising the difference between the phases of the induced voltage and the phase voltage, the current phase difference comprising the difference between the phases of the induced voltage and the phase current, the number of rotations, the output torque, the winding resistance value of the winding and the wiring resistance value of the connection wiring of the brushless DC motor at a predetermined temperature, the compensating value for the voltage phase difference and the current phase difference that has been set in advance depending on the number of rotations and the mechanical loss that has been set in advance depending on the number of rotations, and the phase angle of the induced voltage constant and the induced voltage that has been set in advance depending on the temperature of the rotor; a phase resistance value calculating device (for example, step S 12 in the embodiment described below) for calculating the phase resistance value of the brushless DC motor during rotation based on the winding temperature, the winding resistance value, and the wiring resistance value; a phase difference calculating device (for example, step S 14 and step S 17 in the embodiment described below) for calculating the voltage phase difference and the current phase difference; the phase difference compensating device (for example, step S 16 to step S 19 in the embodiment described below) for calculating the compensating voltage phase difference and the compensating current phase difference that compensate the current phase difference and the voltage phase difference based on the compensating value; a motor out calculating device (for example, step S 20 in the embodiment described below) for calculating the motor output power and motor input power of the brushless DC motor based on the output torque and the number of rotations; a copper loss calculating device (for example, step S 21 in the embodiment described below) for calculating the copper loss based on the phase resistance value and the effective value of the phase current that includes all frequency components; a total motor loss calculating device (for example, step S 22 in the embodiment described below) for calculating the total motor loss by subtracting the motor output power from the motor input power; a subtracting device (for example step S 26 in the embodiment described below) for calculating the iron loss by subtracting the copper loss and the mechanical loss from the total motor loss; an equivalent resistance value calculating device (for example step S 27 in the embodiment described below) for calculating the measured iron loss equivalent resistance value based on the effective value of the phase voltage that includes all frequency components and the measured iron loss; an effective phase calculating device (for example, step S 28 in the embodiment described below) for calculating the current value of the effective phase current eliminating the iron loss component by subtracting the iron loss component from the effective value of the phase current based on the measured iron loss equivalent resistance value and the compensating current phase difference and an effective phase difference calculating device (for example, step S 28 in the embodiment described below) for calculating the effective current phase difference eliminating the iron loss component from the compensating current phase difference based on the magnetic field axis current value and the torque axis current value of said effective phase current; and an inductance calculating device (for example, step S 29 in the embodiment described below) for calculating the magnetic field axis inductance and the torque axis inductance based on the phase resistance value, the number or rotations, the inductance voltage constant, the effective phase current, the compensating voltage phase difference, and the effective current phase difference.
According to the program for detecting the constant of a brushless DC motor having the structure described above, the winding resistance value after temperature compensation can be calculated based on the winding resistance value at a certain temperature and the winding temperature that are read out by the operating data reading device. In addition, the phase resistance value is calculated by adding the calculated winding resistance value and the wiring resistance value, and then the copper loss is calculated from the phase voltage. The iron loss is calculated based on this copper loss, the mechanical loss, and the total motor loss, and then the effective phase current that does not include the iron loss component is calculated by calculating the iron loss equivalent resistance value for the phase voltage.
In addition, the voltage phase difference and the current phase difference are compensated by the compensating value of the voltage phase difference and the current phase difference read out from the operating data reading device, and then the effective phase difference that does not include the iron loss component is calculated.
In addition, each of the inductances can be calculated with high precision taking into consideration the fluctuation of the copper loss, the discrepancy in the phase current due to the iron loss, and the detected error due to the phase delay of the position detecting device by calculating the magnetic field axis inductance and the torque axis inductance based on the induced voltage constant read out by the operating data reading device, the phase resistance value, the effective phase current, and the effective phase difference.